Xiaomei Wang

A novel polar-modified post-cross-linked resin and its enhanced adsorption to salicylic acid: Equilibrium, kinetics and breakthrough studies

Improving the surface polarity is of significance for the post-cross-linked resins to enhance their adsorption to polar aromatic compounds. In the present study, we prepared a novel polar-modified post-cross-linked PDEpc_D by the Friedel-Crafts alkylation reaction and the amination reaction, the Brunauer-Emmett-Teller (BET) surface area and pore volume increased significantly after the Friedel-Crafts alkylation reaction and the surface polarity improved greatly after the amination reaction. Batch adsorption showed that PDEpc_D possessed a much enhanced adsorption to salicylic acid as compared the precursors PDE and PDEpc as well as the non-polar post-cross-linked PDVBpc. The equilibrium data was characterized by the Freundlich model, π-π stacking, hydrogen bonding and static interaction were the possible driving forces. The adsorption was a fast process and the kinetic data obeyed the micropore diffusion model. Column adsorption-desorption experiments suggested that PDEpc_D was a potential candidate for adsorptive removal of salicylic acid from aqueous solution.

Synthesis, characterization, and adsorption properties of phenolic hydroxyl group modified hyper-cross-linked polymeric adsorbent

A kind of phenolic hydroxyl group modified hyper-cross-linked polymeric adsorbent HJ-02 was prepared from macroporous crosslinked chloromethylated styrene-divinylbenzene copolymers by Friedel-Crafts post-cross-linked reaction and esterified reaction. Its chemical structure and pore structure were characterized by chemical analysis, infrared spectroscopy, and N(2) adsorption-desorption experiments. It was thereafter applied to adsorb p-aminobenzoic acid in aqueous solution for its potential application in separation and purification. The p-aminobenzoic acid aqueous solution, pH unadjusted, was the optimum for the adsorption and the salinity posed a positive effect. The adsorption dynamic curves obeyed the pseudo-second-order rate equation and the adsorption was controlled by an intraparticle diffusion model. The adsorption enthalpy was calculated to be negative and decreased with the increase of the p-aminobenzoic acid uptake. The surface character of HJ-02 resin was described with function of the adsorption enthalpy by Dos model and the result indicated that it exhibited surface energy heterogeneity.

Tunable porosity and polarity of polar post-cross-linked resins and selective adsorption

Herein we synthesized three polar post-cross-linked resins by adjusting the initial cross-linking degree of the precursor copolymers, and found that the porosity and polarity of these resins could be effectively tuned. The polar post-cross-linked resin with the initial cross-linking degree of 10% (abbreviated as PVE_10%_pc) possessed a much greater BET surface area and almost all micro/mesopores, but lower content of ester groups, while that with the initial cross-linking degree of 60% (named as PVE_60%_pc) had a much less BET surface area, less micro/mesopores and considerable macropores, but higher content of ester groups. The different porosity and polarity of these resins endowed them with different selectivity for the adsorption of aromatic compounds. PVE_10%_pc owned the largest equilibrium capacity to phenol whilst PVE_40%_pc was the most efficient for adsorption of benzoic acid, and hydrogen bonding, hydrophobic interaction and π-π stacking were the main driving forces for the adsorption.

Bisphenol-A modified hyper-cross-linked polystyrene resin for salicylic acid removal from aqueous solution: adsorption equilibrium, kinetics and breakthrough studies.

In this study, a series of bisphenol-A modified hyper-cross-linked polystyrene resins labeled as HJ-L00, HJ-L02, HJ-L04, HJ-L06 and HJ-L08 were synthesized, characterized and evaluated for adsorptive removal of salicylic acid from aqueous solutions. The structural characterization results indicated that the resins possessed predominant micropores/mesopores, moderate specific surface area and a few bisphenol-A groups on the surface. All the bisphenol-A modified hyper-cross-linked resins were effective for removing salicylic acid from aqueous solutions, and sample HJ-L02 had the largest adsorption capacity. The adsorption equilibrium data were correlated by the Freundlich isotherm model, and a positive adsorption enthalpy was obtained. The kinetic data were analyzed with two diffusion models and indicated that the intra-particle diffusion was the sole rate-controlling step in the first stage. The dynamic experimental results showed that the breakthrough point of the HJ-L02 adsorbent was at 90.2 BV (bed volume, 1 BV=10 mL) for a feed concentration of 500.0mg/L of salicylic acid, and 14.0 BV of 1% of sodium hydroxide could completely regenerate the HJ-L02 adsorbent column.

A novel polar-modified post-cross-linked resin: Effect of the porogens on the structure and adsorption performance.

The porogens used in the polymerization play important roles in the structure and adsorption performance for the polar-modified post-cross-linked resins. A series of novel polar-modified post-cross-linked resins were prepared using different mass percentage of toluene and 3-methyl-1-butanol as the mixed porogens. The results indicated that the resins using a higher mass percentage of toluene in the mixed porogens possessed a higher content of pendent vinyl groups, the greater Brunauer-Emmett-Teller (BET) surface area and t-plot micropore surface area. Whats more, the Friedel-Crafts alkylation reaction induced a higher increment of the BET surface area and t-plot micropore surface area before and after the post-cross-linking. The resin p(GMA-co-DVB)-22-pc using 50% (w/w) of toluene and 50% (w/w) of 3-methyl-1-butanol in the mixed porogens held the largest equilibrium capacity to phenol among the four considered resins. The equilibrium data was well characterized by the Freundlich model and the isosteric enthalpy decreased dramatically with increasing of the fractional loading. The resin using a lower mass percentage of toluene in the mixed porogens required less time to reach equilibrium because of its less micropores and the minor diffusion resistance in the pores. p(GMA-co-DVB)-22-pc exhibited a dynamic saturated capacity of 55.4 mg/mL wet resin at an initial concentration of 1250 mg/L and a flow rate of 1.4 mL/min, and it could be completely regenerated by 0.001 mol/L of sodium hydroxide (w/v) and 80% of ethanol (v/v).

Macroporous crosslinked polydivinylbenzene/polyacryldiethylenetriamine (PDVB/PADETA) interpenetrating polymer networks (IPNs) and their efficient adsorption to o-aminobenzoic acid from aqueous solutions

Macroporous crosslinked polydivinylbenzene/polyacryldiethylenetriamine (PDVB/PADETA) interpenetrating polymer networks (IPNs) were prepared in this study and their adsorption performance was investigated using o-aminobenzoic acid as the adsorbate. The results indicated that PDVB/PADETA IPNs had a large equilibrium capacity to o-aminobenzoic acid, the Freundlich and Sips models were appropriate for fitting the equilibrium data, and the isosteric enthalpy kept constant (about -30 kJ mol(-1)) with the equilibrium capacity at 5-125 mg g(-1). The pseudo-first-order rate equation characterized the kinetic data better than the pseudo-second-order rate equation. At an initial concentration of 593.1 mg L(-1) and a flow rate of 84 mL h(-1), the breakthrough and saturated capacities were 50.62 and 95.70 mg mL(-1) wet resin, respectively, and the resin column could be regenerated by 0.1 mol L(-1) of sodium hydroxide (w/v) and 40% of ethanol (v/v).

Adsorption of p-chlorophenol on three amino-modified hyper-cross-linked resins

Three amino-modified hyper-cross-linked resins (HCP-M, HCP-E, and HCP-D) were synthesized, and they were evaluated for adsorption of p-chlorophenol from aqueous solution. The results indicated that the uploading amounts of the amino groups on the three resins followed an order of HCP-M<HCP-E<HCP-D, while their Brunauer-Emmett-Teller surface area had an opposite order. The three resins were efficient for adsorption of p-chlorophenol from aqueous solution and hydrogen bonding was the main driving force for the adsorption. The isosteric adsorption enthalpy at zero fractional loading had an order of HCP-M (-44.92kJ/mol)<HCP-E (-57.12kJ/mol)<HCP-D (-61.53kJ/mol). At the initial concentration of 502.1mg/L and the flow rate of 68mL/h, the saturated dynamic capacities of HCP-M, HCP-E, and HCP-D were 388.1, 394.3, and 318.1mg/g dry resin, respectively, and these resins could be completely regenerated and repeatedly used.

Synthesis, characterization and adsorption properties of an amide-modified hyper-cross-linked resin

Friedel–Crafts reaction, amination reaction and acetylation reaction were performed with chloromethylated polystyrene (CMPS), and amide-modified hyper-cross-linked resin, HCP-EDA-AA, was prepared. The prepared HCP-EDA-AA owned predominant nanopores and medium polarity, making it possess superior adsorption performance to salicylic acid as compared with the raw material CMPS and the intermediate products, hyper-cross-linked polymer (HCP) and the ethylenediamine-modified hyper-cross-linked resin (HCP-EDA). The Langmuir model characterized the equilibrium data better than the Freundlich model. At a feed concentration of 800.5 mg L−1 and a flow rate of 67 mL h−1, the dynamic capacity of salicylic acid on HCP-EDA-AA was 267.8 mg g−1, very close to the extrapolated value by the Langmuir model (273.9 mg g−1). The salicylic acid adsorbed HCP-EDA-AA resin column was almost regenerated by a mixed desorption solvent including 0.01 mol L−1 of sodium hydroxide (w/v) and 20% of ethanol (v/v). HCP-EDA-AA was repeatedly used nine times and the equilibrium capacity for the ninth time reached 95.5% of the equilibrium capacity for the first time.

A β-naphthol-modified hyper-cross-linked resin for adsorption of p-aminobenzoic acid from aqueous solutions

A β-naphthol-modified hyper-cross-linked resin HJ-G10 was synthesized, characterized, and evaluated for adsorption of p-aminobenzoic acid from aqueous solutions. The adsorption was effective and a higher temperature was more favorable. The Freundlich equation characterized the equilibrium data better, the calculated isosteric enthalpy was positive and decreased with increasing of the equilibrium adsorption amount. The molecular form of p-aminobenzoic acid was favorable for the adsorption and the adsorption in acidic solution was relatively more effective. The pseudo-second-order rate equation fitted the kinetic curves better than the pseudo-first-order rate equation.

4-Vinylpyridine-modified post-cross-linked resins and their adsorption of phenol and Rhodamine B

Herein 4-vinylpyridine (4-VP) was employed as the functional monomer to copolymerize with divinylbenzene using 1,2-dichloroethane (DCE) as the porogen, and a series of 4-vinylpyridine-modified post-cross-linked resins was fabricated. The effect of 4-VP and DCE percentage on the porosity, polarity, and adsorption was investigated in detail. The results indicate that the porosity and nitrogen (N) content of the as-prepared resins can be easily regulated by changing the 4-VP and DCE percentage. Specifically, HPDN-10%-300% with 10u202fwt% 4-VP and 300u202fwt% DCE has the highest specific surface area (SBET) and pore volume (Vtotal), while HPDN-10%-100% with 100u202fwt% DCE has the greatest micropore area (Smicro) and micropore volume (Vmicro). Furthermore, the equilibrium adsorption experiments of the resins exhibit that the adsorption of phenol on HPDN-10%-100% is the most efficient by reason of its greatest Smicro and Vmicro, whereas HPDN-10%-300% owns the largest equilibrium capacity to Rhodamine B (RB) because of its highest SBET, Vtotal, and broad pore size distribution (PSD). The kinetic adsorption reveal that HPDN-10%-100% needs the least time to reach equilibrium for the adsorption of phenol while the adsorption of RB on HPDN-10%-300% is the fastest. The temperature is disadvantageous for the adsorption and the isosteric enthalpy at zero fractional loading is predicted to be -40.39 and -56.38u202fkJ/mol for phenol and RB on the resins, respectively.